Chapter 67 Leading edge slats (25)
As we all know, the J-8 series fighter jets have poor low-altitude and low-speed performance.
In addition to the poor performance of the turbojet engine itself at low altitude and low speed, a more important reason is that due to objective constraints, the aircraft chose a rather simple wing configuration during design.
There is no leading edge device, and the trailing edge is just the most common traditional flap.
This type of flap easily separates from the suction-producing side due to its flow, and its wake is unstable. Flow separation occurs on the flap at medium deflection angles, and its lift-increasing capability is very average.
However, from another perspective, a low starting point means there is a lot of room for improvement, which is not necessarily a bad thing for the current Chang Haonan.
Only this time, there is no experience for future generations to draw from.
Therefore, he has not yet decided whether to install leading edge flaps or leading edge slats.
The leading edge slat has a better lift effect, but the structure is more complex and it also brings greater noise.
Of course, this is just a general rule, and the specific performance must ultimately be implemented at the design level.
Generally speaking, there are advantages and disadvantages between the two, and it mainly depends on how to choose.
Hearing Chang Haonan's idea of extending the aileron hinge fairing into a trailing edge wing blade, almost everyone present brightened up.
But when they heard about the leading edge lifting device, many people showed expressions of hesitation.
Finally, it was Liu Ming who concluded:
"Comrade Xiao Chang's ideas about the design of the wing knife are indeed very good."
"As for the leading edge lifting device..."
Liu Ming and Yang Fenghata, who was sitting in front, looked at each other:
"In fact, when the 80 Project was still in the pre-research stage, around the end of the 8s, we collaborated with the French company Dassault to design a leading edge slat, which was intended to be used to improve the J-2- aircraft at that time."
This is something Chang Haonan has never heard of before.
"Yes, Mr. Gu also said at the beginning that if the J-8 can be equipped with a suitable set of leading edge slats, the overall performance will not be weaker than the Mirage 2000." Yang Fenghata also recalled:
“It happened to coincide with the honeymoon period of our cooperation with the French in the aviation industry, and a joint study was launched, probably at the same time as the Peace Model Project.”
When Yang Fenghata mentioned the words "model of peace", the air pressure in the entire venue instantly dropped a little.
That story can be called a shame for the Chinese aviation industry. In the mid-80s, nearly US$6 million in currency value was wasted. Two aircraft were impounded for several years without reason before they were returned to China in parts.
Some pro-American media in later generations even shamelessly promoted this plan as the so-called "starting point for the modernization of China's aviation industry"!
In fact, a large part of the reason why the August 3rd Project was approved and received so many resources was because of the shameful failure of this model peace plan.
We want to build a competitive fighter, a fighter that can prove that we can do it without the help of Americans!
"Well...how was the design completed at that time?" Chang Haonan asked.
"Honestly, it's not very good." Yang Fenghao shook his head:
"We have been working with Dassault engineers for about two years, but the final design version still failed to achieve the performance that the French originally expected."
"On the one hand, the structure is a bit too complex, and on the other hand, there is a lack of sufficient design tools. During wind tunnel testing, we found that there is always interference between the leading edge slats and trailing edge flaps, resulting in a lower lift effect. Only when the flaps are on.”
This result was not what Chang Haonan expected.
The biggest gain from Sino-French cooperation is that our country has learned a complete set of aviation industry standards from the other country, and finally formed a complete national military standard in the air force field with reference to French military standards.
But specifically in terms of technology, there are really not many results that can be achieved, that is, there are only a few types of Z-9 helicopters and Sidewinder anti-aircraft missiles.
The design of the Agosta 90B submarine proved to be completely inferior to the Kilo.
The Super Hornet helicopter has been tinkered with for nearly 40 years. In the end, a new model was almost designed from scratch before being deployed on a large scale under the name of 8G/L.
The 100mm naval gun, which is considered to be able to unify the main gun types of large and medium-sized surface ships, is even more of a sinkhole. After only being briefly equipped with about a dozen ships, the 100mm caliber was completely replaced by the 130/76 caliber.
It’s not that the French are deliberately doing evil, it’s actually that they themselves were walking on these crooked roads back then...
In short, given these precedents, it does not seem very surprising that a leading edge slat design does not work well.
But having said that, Dassault is indeed experienced in the design of large delta wings. From Mirage 3 to Mirage 2000, a variety of classic tailless delta wing aircraft were designed by Marcel Dassault.
So Chang Haonan was a little interested in the design they gave.
"Mr. Yang, I wonder if there are still archives of Dassault's designs from back then?"
"Are you going to improve their slat design?" Yang Fenghao asked, playing with the pen in his hand.
"It may not be an improvement." Chang Haonan shook his head:
"You may need to start the design from scratch, but it is always good to refer to the experience of the French."
"The performance of slats in increasing lift is better than that of leading edge flaps. As for the design, I think since ten years have passed, many problems that could not be solved back then may not be problems now."
When Chang Haonan first arrived at Institute 601 a dozen days ago, if a young man in his early twenties dared to boast that he would complete a slat design that even the French had not done, most people would have scoffed.
But now, considering the amazing abilities Chang Haonan showed before, the first reaction of most people in the venue was that this thing might be possible!
……
About an hour later, the long-dusted leading edge slat design data was taken out of the data room of Institute 601 and sent to the conference room.
For such a serious work as aircraft design, the so-called design data cannot be just a design drawing, but two boxes filled with calculations and explanation documents.
Of course, Chang Haonan doesn't need to see all of these things. His focus is firstly on the design plan itself, and secondly on what difficulties the French and the 601 Institute encountered back then, so that they could not even complete the paper design process.
However, when Chang Haonan opened the overall design drawing and saw the complicated three-stage leading edge slat design, he almost subconsciously uttered a curse word.
"Holy shit, why is this a plan?"
That's right, Chang Haonan had seen the slat design that was almost exactly the same as the one on the drawing before he was reborn.
But it was neither on the Chinese plane nor on the French plane.
But on a plane in India...
The LCA "Tejas" fighter jet, which was designed in 1983 and was not put into service until 2016, had a tailless delta wing layout designed by Dassault.
The LCA's leading edge slat is this precise and complex three-stage structure.
Now it seems that 80% of the time it was Dassault who perfected the semi-finished product after returning and stuffed it directly into LCA...
